DESCRIPTION: The Investigator requests three additional years of funding to investigate how oropharyngeal and postingestional food-related stimulation interact and influence behavior. Previous work by the Investigator has revealed that the initial rate of licking of a test solution is a linear function of the log concentration of a variety of different carbohydrates and oils. The rate of decline of the rate of licking is a linear increasing function of the log of carbohydrate concentration and an exponential increasing function of the log concentration of corn oil. It is the combination of these two effects on the licking behavior of the rat, one acting at the oropharyngeal level and the other at the post-ingestive level, that determines how much will be ingested in a short-term test; i.e., a meal. All of these parameters can best be determined by investigation of the microstructure of licking; i.e., by analyzing the size of bursts of licking, and the pauses between bursts have been shown to be highly correlated with these. The Investigator now proposes to determine the role of various branches of the vagus in conveying information pertinent to this behavior to the CNS; the nature of specifically gastric stimulation in controlling meal size; the basis for conditioned control of the overall intake; and the properties of certain oils that alter responding.